1. Field of the Invention
The present invention relates to a semiconductor device including a transistor, a method of manufacturing a semiconductor device, and an electronic apparatus.
2. Description of the Related Art
As a form of a semiconductor device, a solid-state image sensor is known. Examples of a typical solid-state image sensor include a CCD image sensor and a CMOS image sensor. The solid-state image sensor of this type has a noise characteristic as a pixel characteristic. Noises of a solid-state image sensor are roughly classified into a random noise and a fixed pattern noise. Further, examples of a typical random noise include a dark current shot noise, an FD (floating diffusion) reset noise, an FD amplifier noise, and a light shot noise.
Further, causes of the noise arise from the following items (1) to (4):                (1) a deep level of a forbidden band of silicon,        (2) a thermal noise in a case where a capacitance C is charged,        (3) a level of a gate insulating film of a transistor of an amplifier that forms an FD amplifier, and        (4) a property of a photon inherent in light.        
Out of those items, in a recent solid-state image sensor, a noise due to the above item (1) has become negligibly small. Further, a noise due to the above item (2) can be suppressed in a circuit. Therefore, the noise of the solid-state image sensor is caused dominantly due to the above item (3). In a case where an amount of light is large as an image-taking condition, a noise due to the above item (4) may be more marked than the noise due to the item (3).
Against such a technical background, there has been proposed a technique that reduces an interface state of a gate insulating film of a transistor formed on a device substrate of a semiconductor device by supplying hydrogen. In addition, there has been proposed a method of reducing an interface state of a gate insulating film by supplying hydrogen in order to recover Swing or Vth (threshold voltage) of a transistor in a semiconductor device having a TFT structure in which a polysilicon thin film is used or in a semiconductor device that uses an SOI substrate. For example, Japanese Patent Application Laid-open No. HEI7-94746 (hereinafter, referred to as Patent Document 1) discloses a technique that supplies hydrogen to a gate insulating film under a gate electrode by setting an oxide film formed on the gate electrode to be thin enough to allow hydrogen to diffuse therein. It should be noted that the TFT is an abbreviated name of a “thin film transistor”, and the SOI is an abbreviated name of a “silicon on insulator”.
In the technique disclosed in Patent Document 1 mentioned above, in the case where hydrogen is supplied to the gate insulating film of the transistor, various films (such as an interlayer insulating film, a barrier metal film of a wiring layer, and a diffusion prevention layer of a copper wiring) formed on an upper layer of the transistor exist as films that hinder the supply of hydrogen. Therefore, there is a problem in that hydrogen is difficult to be efficiently supplied to the gate insulating film.
In view of this, Japanese Patent Application Laid-open No. 2008-108769 (hereinafter, referred to as Patent Document 2) discloses a technique of grinding or polishing a back surface of a semiconductor substrate, on a front surface of which a transistor is formed, to thin the semiconductor substrate, and thereafter supplying hydrogen to a gate insulating film of a transistor from the back surface of the semiconductor substrate.